Erectile dysfunction or impotence is a widespread disorder that is thought to affect about ten to fifeteen percent of adult men. Some pharmacological methods of treatment are available. Such methods, however, have not proven to be highly satisfactory or without potentially severe side-effects. Papaverine is now widely used to treat impotence, although papaverine is ineffective in overcoming impotence due, at least in part, to severe atherosclerosis. Papaverine is effective in cases where the dysfunction is psychogenic or neurogenic and severe atherosclerosis is not involved. Injection of papaverine, a smooth muscle relaxant, or phenoxybenzamine, a non-specific antagonist and hypotensive, into a corpus cavernosum has been found to cause an erection sufficient for vaginal penetration however, these treatments are not without the serious and often painful side effect of priapisim. Also, in cases where severe atherosclerosis is not a cause of the dysfunction, intracavernosal injection of phentolamine, an .alpha.-adrenergic antagonist, is used. As an alternative or, in some cases, an adjunct to .alpha.-adrenergic blockade, prostaglandin E1 (PGE1) has been administered via intracavernosal injection. A major side effect frequently associated with intracorprally delivered PGE1 is penile pain and burning. Thus, there is a need for treatments of human male impotence without the undesirable side effects of those agents currently used.